Method for Making Non-linearly Elastic Composite Systems

ABSTRACT

The present invention discloses a method for making and use Non-linearly Elastic Composite Systems wherein said non-linearly elastic composite systems comprises non-linearly strain changes in beam height during bending.

BACKGROUND OF THE INVENTION

It is well known that, the imperative advantages of composite systems,as lightness and good specific strength, wherein said “specificstrength” in Composite Materials is defined as ratio of the strength tothe density.

Generally, in some specific composite systems, the main components areLattice, fibers and/or strands, and matrix. These components'combination and interaction in the mentioned arrangement leads to anintegrated operator unit having its particulars.

Meanwhile, in some Non-linearly Elastic Materials (such as, plastics andwoods), strain changes in beam height during bending, is mainlynon-linear, wherein said strain changes could cause high modulus ofresilience (energy absorbing capacity) and resistivity (specificstrength) in bending.

High modulus of resilience and significant strength in bending,particularly when they accompany with weight and dimensions reduction,are crucial. Moreover, the mentioned specifics could lead to betterbehavior and ultimate strength against in bending forces, disseminatedimpacts, shock and vibration. For instance, these characteristics areimportant in constructing load-bearing, lightweight pieces and slabs (inbending), elements exposed to vibration, impact, shock and in bendingforce, in building, bridge, road, and “Railroad & Subway” structures.

Therefore, it would be advantageous to increase the modulus ofresilience and specific strength in bending. The present inventiondiscloses a method for making composite systems with non-linearly strainchanges in beam height during bending.

SUMMARY OF THE INVENTION

The present invention discloses a method for making and use Non-linearlyElastic Composite Systems wherein said non-linearly elastic compositesystems comprises non-linearly strain changes in beam height duringbending, wherein said method further comprises steps of:

Creating dispersed suitable pores, and/or appropriately distributingsuitable materials and particles, wherein said suitable material andparticles characterized in that lower strength comparing with contextmatrix;

obtaining resilient composite systems wherein said resilient compositesystems is a type of composite arrangements and materials, in which,strain changes in beam height during bending is non-linear, and whereinsaid resilient composite systems consist at least of; a) Suitablelattice or lattices with expedient shapes and directions; b) Fibers orstrands with expedient flexibility; c) Conjoined suitable matrix havingdispersed pores and/or disseminated expediently flexible beads orparticles;

combing and interacting said a) Suitable lattice or lattices withexpedient shapes and directions; b) Fibers or strands with expedientflexibility; and c) Conjoined suitable matrix having dispersed poresand/or disseminated expediently flexible beads or particles, therebyleading to non-linear changes in beam height during bending.

BREIF DESCRIPTION OF THE DRAWINGS

FIG. 1) Shows a simple Instance of a Type of Resilient Composite System;R.C.S., Having Non-linearly Strain Changes during Bending (as aNon-“linearly Elastic Material).

FIG. 2) shows an example of the Elastic Composite, ReinforcedLightweight Concrete.

FIG. 3-a) Shows as an Example of the Stress-Strain Diagram of inCompressing Loading of a Similar Instance of above said Fibered FlexibleLightweight Concrete, Which Used as a component of mentioned ElasticComposite, Reinforced Lightweight Concrete (Oven-dry Density≈600 kg/m3,f′c≈29.5 kg/cm2 in 28 days, Monofilament Polypropylene Fiber; about 1.1%of Volume Concrete).

FIG. 3-b) an Instance of the Fibered Flexible Lightweight Concrete afterCompressing Loading.

FIG. 4 a) An Instance of the Execution Manner of a Type of the CeilingUsing Said Elements and Components. (In Form of the Usual Ceilings,Called as Composite.)

FIG. 4 b) Detailed illustration of an Instance of the Execution Mannerof a Type of the Ceiling Using the Elements and Components. (In Form ofthe Usual Ceilings, Called as Composite.)

DETAILED DESCRIPTION OF THE INVENTION

In preferred embodiment, the present invention discloses a method formaking Non-linearly Elastic Materials in framework of disclosedcomposite arrangement (“Resilient Composite Systems; R.C.S.).

As shown in FIG. 1, the Resilient Composite Systems consist of at least;a) Suitable lattice or lattices with expedient shapes and directions; b)Fibers or strands with expedient flexibility; c) Conjoined (consistent)suitable matrix having dispersed pores and/or disseminated expedientlyflexible beads or particles. The particular components' combination andinteraction in the system leads to non-linear changes in beam heightduring bending in practice, as the specific functional character ofthese systems.

Thus, the disclosed composite systems is made by creating dispersedsuitable pores, and/or by appropriately distributing suitable materialsand particles (with lower strength comparing to the context matrix) inthe reinforced, fibered matrix, which could have expedient elasticity.The purpose is to achieve a specific functional character withnon-linear strain changes in beam height during bending in the systemswith reticular arrangement, as integrated operator units. An example ofmaking R.C.S implementing the method of the present invention:

Generally, “Elastic Composite, Reinforced Lightweight Concrete”, havingnon-linear strain changes in beam height during bending, high modulus ofresilience and bearing capacity “in bending”, is also a type ofResilient Composite Systems; R.C.S.).

Said “Elastic Composite, Reinforced Lightweight Concrete” (named also asResilient Composite Concrete; R.C.C.) is a particular fibro-elastic,reinforced lightweight concrete with a kind of reticular arrangement,having the said functional character during bending.

In this special composite system, the matrix is a particular type oflightweight concrete (or cement paste). The disclosed lightweightconcrete (or cement paste) has dispersed pores and/or flexibleaggregates (for instance, Polystyrene Granules, etc) in the consistentcement material in suitable content (which leads to providing expedientbehavior). Thus, said “Elastic Composite, Reinforced LightweightConcrete” has been consisted of the said lightweight concrete (or cementpaste), appropriate lattice or lattices (for example, welded steel wiresmeshes, etc) and fibers (such as partially elastic Polymer fibers likePolypropylene fibers, etc), in an expedient arrangement for achievingsaid specific functional character (non-linear strain changes in beamheight during bending). It is worth stating that in the usual reinforcedconcrete beams, strain changes in beam height during bending, areassumed “linear”, and the current applied relations and calculations arebased on this basic assumption.

In said composite, reticular arrangement, the existed pores and/orlightweight flexible aggregates or beads, accompanied by the appropriateroles of the other components in the system lead to the requiredflexibility, resilience and ductility in the system, whereas inconventional lightweight concretes pores and/or lightweight flexibleaggregates or beads tends to brittleness. Nevertheless, the generalobjective of employing fibers and lattices in said composite structureis substantially similar to the one in conventional concretes (such asfibered concretes, Ferro cements, etc).

Said structure, in view of its texture and special pattern of strainduring bending, has more specific strain capability (particularly inelastic range), energy absorbing and load bearing specific capacities inbending comparing to the usual reinforced concrete beams.

In under-bending sections of said elastic composite, reinforcedlightweight concrete, the established deformities in conjoined andperpendicular to load applying direction layers during bending, theinitially plane and perpendicular to beam axis sections are removed fromplane and vertical state to curve shape during bending

Thus, the basic geometrical assumption of bending in the usualreinforced concrete beams based upon linear being of strain changes inbeam height during bending, and its resulted trigonometric equations &equalities are being overshadowed.

The present invention provides better distribution of internal stressesand reduction of their partial concentration in certain areas of thesection during bending course. For instance, increasing compressivestresses particularly in the upper part of compressive block in thesection during bending significantly decrease. Meanwhile, the employedmesh and fibers, in their turns increase the elasticity and tensilestrength of the reticular structure. The disclosed strain pattern andbehavior in bending in present system in its turn increases absorption,and control capabilities of applied stresses, and increases enduranceagainst the stresses, and further increases elastic strain capabilityand modulus of resilience of the system in bending.

In said elastic composite, reinforced lightweight concrete, the usualcalculation of equilibrium steel amount for attaining to low-steelbending sections with secure fracture pattern and its relatedlimitations, do not become propounded due to the non-brittle being offracture pattern and non-linear being of the strain changes duringbending. Therefore, solutions for solving some important problems oflightweight concretes applications, such as deadlock of brittle andinsecure fracture patterns in many of the usual reinforced lightweightconcrete structures, is presented. Accordingly, achieving high bearingcapacities in bending elements, and attaining qualitative development ofcapabilities of using lightweight concretes, especially lightweightconcretes with oven-dry densities of <1350-1400 kg/m3 and compressivestrengths of <14-17 mpa, and even with oven-dry densities of <800 kg/m3,are conceivable.

Thus, the present invention has numerous applications in Road andBuilding Industries too. For example, the present invention increasesresistance and safety against earthquake by Lightweight & IntegratedConstruction.

Yet in another application, the present invention provides a system thatis especially useful in seismic areas, and can also be employed inconstructing vibration absorber non-bearing or bearing pieces andelements, which could also be used in Road Construction and “Railroad &Subway Structures” (such as Slab Tracks, Traverses, etc).

“Elastic Composite, Reinforced Lightweight Concrete”, having “strainnon-linear changes in beam height during bending”, high modulus ofresilience and appropriate flexibility in bending, is a fibro-elastic,reinforced lightweight concrete with reticular structure. In the presentinvention, strain changes in beam height during bending, similar to someNon-linearly Elastic Materials, and contrary to the usual reinforcedconcrete beams and so-called Linearly Elastic Materials, is particularlynon-linear.

As disclosed, said structure is a type of particular composite systemscalled generally as “Resilient Composite Systems; R.C.S.”. Thecomponents' combination and interaction in the Resilient CompositeSystems with the mentioned reticular arrangement is so that, it leads tonon-linear changes in beam height during bending, as the specificfunctional character of the present invention.

In Elastic Composite, Reinforced Lightweight Concrete, the matrixincludes a type of flexible lightweight concrete. The lightweightconcrete has pores and/or flexible aggregates (such as PolystyreneGranules, etc), and conjoined (consistent) cement material, inappropriate content, which leads to provide required bonding andadherence. The lightweight concretes containing the Polystyrene granulesare also called as <<EPS concretes>>. Generally, the type of lightweightconcretes having Polystyrene granules, and those called as cellularLightweight concretes with net cement, etc, are partially well known. Aswell, these are being indicated also in ACI 523.IR-92, accompanied withother types of Lightweight concretes. (Generally, usual lightweightconcretes in ACI 523; Ferrocements in ACI 544, and fibered concretes inACI 549 are being discussed.)

In said structure, because of integrated, reticular arrangement, andutilized components behavior and proportion in interaction with eachother, possibility of more appropriate distribution of stresses andstrains is forgathered, and energy absorption and reserving capacitiesare high. Meanwhile, appropriate strain capability particularly inelastic extent brings about possibility of more appropriately attainingstresses and strains in steel and concrete simultaneously and also delayin establishment and out spreading of cracks and effective damage in theconcrete (matrix). This means more benefiting from tensionreinforcements potential capacities. Thus, besides providing suitablestrength reserving and ductility, and fine (non-brittle) anddisseminated being of fracture pattern, accessing to “high capacity ofloading in bending”, despite low weight and dimensions, is achieved.

The organized reticular structure in the context of the utilizedlightweight concrete can also assist to control and accumulation ofcement materials contractile stresses in piece; just as, this mattercould in its turn and in appropriate conditions lead to partiallyincreasing strength of the beam made with this system during tension andbending, and could effect on its ductility. (FIG. 2 & FIG. 3)

As is illustrated in FIG. 2, in an Example, at the time of in bending &in compressive loading tests (in the manners similar to ASTM E 72),f′c≈64 kg/cm2, fr≈34.5 kg/cm2, fct(Brazilian Method)≈14.5 kg/cm2;Es≈2×106 kg/cm2, Ec≈4×104 kg/cm2; (The lattice is made of cold-drawnsteel wires) fyl(Mesh)≈4672 kg/cm2, As1(Mesh)≈0.98cm2 −fy2(Bar)≈4400kg/cm2, As2(Bar)≈2.26cm2; d1(Mesh)≈3 cm, d2(Bar)≈3.9cm, L≈120 cm, h≈5cm, b≈100 cm. Portland cement (type II)+Silica fume (8.5% of cementmaterials)≈675 kg/m3; W/C+S≈0.425 (with using Lignosulfonate as a common“plasticizer” and retardant); Fibers (Polypropylene, denier: 3, and intwo different lengths: 2 portion in 12 mm & 1 portion in 6 mm)≈12.6kg/m3; Expanded Polystyrene Granules (D50≈3.2 mm) up to 1 m3. Notes: Noother materials, additives and aggregate are used in the lightweightconcrete in said example; membranous curing has been performed in therelated environmental conditions; the lightweight concrete oven-drydensity≈835 kg/m3; drying shrinkage of the employed high fiberedlightweight concrete (90 days)<0.015, and some loading tests have beendone about 3 months after making the slabs.

As is illustrated in FIG. 3 a, in said flexible lightweight concrete asan Example, Oven-dry Density≈600 kg/m3, f′c≈29.5 kg/cm2 in 28 days,Monofilament Polypropylene Fiber; about 1.1 % of Volume Concrete.

As is illustrated in FIG. 3 b, some noticeable particulars of saidinstance of the mentioned fibered flexible lightweight concrete (as anexample) are: appropriate ratios of elasticity modulus and tensile andshearing strengths to compressive strength; suitable ratios of thesurface under stress-strain diagram and strength in “elastic limit” toultimate strength (especially, “noticing the concrete density”);expedient ductility, and high being of the strain correspondent withstrength peak, the strain correspondent with failure (εcu) and fracturetoughness (high α and β stress block indices), and non-fragile being andoccurrence of a type of being compressed (in high compressive loadings).[In this case, it is worth mentioning that in the view of theconsiderable failure toughness, and occurrence of a type of graduallycrashed being in the lightweight concrete pointed here as an example(especially of fibered type) instead of the typical outspreadingshattering occurred failure about some usual lightweight concretes,here, the subject of “the strain correspondent with failure (ε_(cu))”(in its current, as a certain, exact quantity) loses its particularpoint.]

Considering the results of accomplished actual loading the above elasticcomposite, reinforced lightweight concrete, analysis of the mentioned“in bending” structures upon assumptions and equations related to theusual reinforced concretes in calculating nominal ultimate strengthmoment (Mn) with the method called as “ultimate strength”, the obtainnumbers have been much less than the attained actual amounts of inpractice (M_(e)). Even when concrete's compressive strength in therelated equations, from mathematical point of view is tended towards<<∞>>, and have considered the strain block height equal to zero, theM_(e) has been obviously higher than M_(n). Particularly, “actualamounts of strain in bending in elastic limit” and therefore, “modulusof resilience” (u=½ σy.εy) have been considerably higher than theexpected amount based upon relations related to the usual reinforcedconcrete beams (with basic assumption of strain linear changes in beamheight during bending). In fact, in view of the certain manner of strainchanges in beam height during bending, despite considerable increase ofapplied tensile forces in the slab in bending course from what isusually called compressive block strength in the usual reinforcedconcrete beams, strain is yet being continued up to reaching to higherstrains. Meanwhile, occurrence of bending fracture in the slab has beenresulted from gradual incidence and deepening of cracks in under graterstretch layers in the beam, after passing from elastic and plasticstage, with a non-brittle pattern. Furthermore, despite significantlyhigher being of the utilized tensile steel amount in the mentioned slabof equilibrium steel (calculated <<pb>>according to common relationsrelated to the usual reinforced concrete beams (εcu=0.003)), still thefracture pattern in the loaded pieces has not become “primarycompressive” type and brittle.

The bending pattern in this system differs from the usual reinforcedconcrete beams. Thus, in these structures, the logical necessity ofequivalence of computable compressive and tensile forces resultants inthe structure during bending (“when the resultants calculated with theusual equations related to the usual reinforced concrete beams”), andits certain resulted trigonometric similarities and the relatedrestrictions, are insubstantial. As well, also considering thenon-brittle being of fracture pattern in the said loaded pieces, even ofprimary compressive type in some of axial loadings, the usualcalculations of equilibrium steel amount to attain low-steel bendingsections with non-brittle fracture pattern (of secondary compressivetype) and its related limitations have no indication of beingpropounded. Thus, the usual serious restriction in benefiting tensilereinforcements in beams and slabs, has been eliminated. Meanwhile, theusual relations for calculating in bending beam nominal capacity (Mn)will result much lesser amounts of in practice actual amount(Me)—particularly that cracking moment (Mcr) and stress amount andespecially, “actual amount of strain in elastic extent” (σy & εy) areconsiderably higher than calculated amounts based upon the usualequations related to usual reinforced concrete beams.

It should be mentioned that even in some of compressive (column-like)loading of the tested pieces, which steel lattices and additionalsupportive bars positions in them have been towards convex surface inthe axial loading, and also regarding the concrete compressive strength,the related slenderness ratio, and load exertion amount and method,fracture of “primary compressive” type has been occurred, because of thecertain lightweight concrete's texture and behavior, yet the fracturepattern has been significantly fine (non-brittle).

Thus, in the above mentioned system, which is behaving as an integratedbeam in its major strain during bending, in addition to appropriateductility, the Elastic Strain Energy and Modulus of Resilience areconsiderably increased, and regarding comparatively high being of StrainEnergy Density, specific capacities of energy reserving and absorptionare high.

Moreover, the reticular structure role on rising strength reserving andconfronting with formation, development, deepening and changing ofvertical and diagonal cracks, the special manners of strain andelasticity, diminish of the accumulating effect of bending moment andtensile force in the beam, and expedient strength against piece lengthalteration, could be in their turns effective on partially increasingthis system strength also against shearing and torsion.

Furthermore, if necessary, simultaneously employing some methods andaccompanying elements such as supportive reinforcements, connectionstrips, foam pieces, reinforcing in different levels in proportion withthis system could be according to the case taken into consideration. Forinstance, in addition to the afore-said impressions of the probablyemployed supportive reinforcements, the supportive bars placed near thefinal tensile strands in the slab, in case of having suitable embedmentand anchor from two directions (e.g., on the accessory or secondarybeams), could accordingly improve the construction's totalityintegration, by assisting in combined function of the mentioned piecewith some other construction elements such as probable so-calledsecondary beams utilized in ceiling. For instance, possibly employingsupportive bars under the used lattice in the mentioned slab cannaturally be impressive on all parts of stress-strain diagram, such asascending branch slope (as “rigidity” and modulus of elasticity) andenergy absorbing capacity, ductility, strength, fracture toughness, andultimate strength energy, in bending [Uu=(σy.σu/2)εu].

Moreover, fibered being of the said flexible lightweight concrete andits adhesive matrix bonding (considering the used components type andamount in that example), and extensive surface of the utilizedreinforcements in shape of lattice with connected, perpendicularlongitudinal and transverse components, are altogether impressive onincreasing involvement of reinforcements in the mentioned lightweightconcrete. Meanwhile, in the view of mixture plan of the above saidflexible lightweight concrete, particularly, the utilized fibers withsuitable involvement in the concrete's bonding and adhesive contextmatrix, and the system reticular structure, result in useful control ofshrinkage effect and the like. The controlled shrinkage could in itsturn assist to increase of fibers and lattice involvement in the contextmatrix. [According to used components and composition of the above saidfibered flexible lightweight concrete in its mixture plan, andconsidering the texture and qualities of this integrated structure andits conjoined (consistent) matrix, it could have suitable durabilityagainst some of destructive agents in long-term.]

Some Applications of said system comprises:

-   -   Constructing various types of slabs, and flat, slope and        dome-shaped ceilings, having high specific bearing capacity in        bending with appropriate security. (FIG. 4)

FIG. 4 is an illustration of an instance of the Execution Manner of aType of the Mentioned Ceiling with Using the Said Elements andComponents (In Form of the Usual Ceilings, Called as Composite.)

Meanwhile, some benefits of employing this system in constructing thebearing lightweight pieces and slab tracks under railways and subwaysare: increase of beneficial lifespan, decrease of structures' dimensionsand weight, saving in spent expenses, time, and energy for repairs,maintenance, possibly replacement, foundation, transportation &implementation.

-   -   Producing “integrated, insulant, lightweight internal and        external walls” with appropriate behavior against impact, shock        and blast. For instance, the non-bearing walls, as the types of        reinforced sandwich panels, could be constructed by easily        executing the paste-form, adhesive, work-able type of this        lightweight concrete (occasionally with less fibers) on with or        without fire retarded foam tri-dimensional meshes having        appropriate stability and flexibility. This practical        implementation technique could easily spread, considering a        partially similar and common existing method of constructing (as        employing the combination of tri-dimensional panels with usual        fine aggregate concrete). These walls and constructional        technology could have the advantages such as: providing more        rapidity & easiness in transportation and installation; little        materials wasting in implementation and least required        additional plasters (considering the suitable surface of the        performed concrete); capabilities of cutting, nailing, and        holding plaques & corpies, and having possibility of repair,        installation transferring, and establishment of frames, doors &        windows, and various coatings & paints; appropriate flexibility        and having possibility of adaptation with diverse architectural        designs (e.g. in curve surfaces and forms). Generally, there are        considerable benefits in using this system and its components in        buildings, especially in a wide view. At least comprising:        significant reduction in construction weight (sometimes up to        3-6 times comparing with some usual heavy materials) and saving        in the related expenses; improvement of resistance, safety and        behavior against earthquake, shock and explosion; suitable        thermal insulation, and sound intervening; increase of indoor        useful space (owing to some components' dimensions reduction);        perform-abilities and capabilities of the so-called in-place,        precast and semi-precast implementations (according to the        case); etc. These benefits could in their turns have imperative        importance also in constructing high buildings and towers,        constructing in seismic and/or far-reaching areas.    -   Strengthening and safe-making some constructional elements, for        example in bending and shearing, and coiling the columns        circumference for improving their ductility, fracture strength        and bearing capacity. It is worth mentioning that according to        the specified instruction, employing this composite structure in        the columns circumference (with appropriate connection,        extension and bonding), can be useful in confronting with crack        formation, scaling and pitting in the circumference of high        axial under-load columns, and buckling phenomenon in them. As        well, appropriately using this system can in its turn increase        ductility, fracture strength and bearing capacity in columns,        also by applying effective radial stress from circumference to        the center.    -   Employing in construction of road, bridge, and especially, Slab        Tracks & Traverses and non-bearing or particularly, “bearing”        vibration absorber, lightweight pieces under Railways and        Subways.

Generally, referring to reticular system's specialties, as appropriateenergy absorbing capacity, elastic strain capability and “EnduranceLimit” in bending, and suitable behavior against dynamic loads anddisseminated impacts and shocks, the present invention is beneficiallyemployed for constructing vibration and shock absorber and exposed tocontinual dynamic loads pieces too.

It is understood that various changes or modifications can be madewithin the scope of the appended claims to the above Resilient CompositeSystems without departing from the scope and the spirit of theinvention. The principle of this invention is not limited to theparticular embodiments described herein. Various embodiments can employthe present invention. This invention is not limited to the exactillustration as described; alternative methods can be used to form theintended Resilient Composite Systems and the method for making same ofthis invention.

1. A method for making and use Non-linearly Elastic Composite Systems,wherein said non-linearly elastic composite systems comprisesnon-linearly strain changes in beam height during bending, and whereinsaid method further comprises steps of: Creating dispersed suitablepores, and/or appropriately distributing suitable materials andparticles, wherein said suitable material and particles characterized bylower strength comparing with context matrix; obtaining resilientcomposite systems wherein said resilient composite systems is a type ofcomposite arrangements and materials, in which strain changes in beamheight during bending is non-linear, and wherein said resilientcomposite systems consist of at least; a) Suitable lattice or latticeswith expedient shapes and directions; b) Fibers or strands withexpedient flexibility; c) Conjoined suitable matrix having dispersedpores and/or disseminated expediently flexible beads or particles;Combining and interacting said a) Suitable lattice or lattices withexpedient shapes and directions, b) Fibers or strands with expedientflexibility, and c) Conjoined suitable matrix having dispersed poresand/or disseminated expediently flexible beads or particles, therebycreating non-linear changes in beam height during bending.
 2. The methodas claimed in claim 1, wherein said method further comprises step of;obtaining high modulus of resilience and resistivity in bending, therebyincreasing capacity of bearing in bending.
 3. The method as claimed inclaim 1, wherein said Resilient Composite Systems characterized in thatElastic concrete, Composite concrete, Reinforced concrete andlightweight concrete with non-linearly strain changes in beam heightduring bending.
 4. The method as claimed in claim 1, wherein saidResilient Composite Systems is employed in construction field, marinestructures and floaters, rail roads, bridges, roads, highways, andvehicles.
 5. The method as claimed in claim 1, wherein said ResilientComposite Systems performs the act of shielding and absorbing shockresulting from an explosion.
 6. The method as claimed in claim 1,wherein said Resilient Composite Systems is employed in making objects,wherein said objects comprises facade covers, lumber, cabinet, counter,and pip and ducts.
 7. The method as claimed in claim 1, wherein saidResilient Composite Systems is employed in making wall partitions andcovers in reservoirs.